If you've run into some odd bow-tie shaped screw slots on your window or door hardware, you have probably discovered clutch head screws.  They were used in the auto industry from the 1940s through the 1960s and a few of them worked their way into travel trailer manufacturing as late as the 1970s.  To remove those old screws, you're best off using a screwdriver bit of the same shape and size. 

Our set of clutch head bits includes the two most commonly used sizes on vintage travel trailers: 5/32" and 3/16" sizes. You can check size by measuring the maximum diameter in inches of the slot.

The bits fit in your power drill or a hand screwdriver that accepts interchangeable 1/4" hex bits.